Motors stopped arming

Installed the Zenmuse Gimbal H3-2D last week. Everything was going great but within the week something happened.

Now I can't get my motors to start up. I have the double-blinking, ready-to-fly green lights. My controller is still in contact (lights turn yellow or red when I turn it on and off and I can tell my quadcopter to calibrate the gps) but when I pull both sticks down - nothing.

The blades all rotate fine and there was no crash that started this. Just one time it was working, the next it wasn't.

Nothing else changed at all? No upgrades to firmware, charging glitches with a battery, environmental changes....
I got nothing; just throwing out ideas here.

If it were me, and it isn't, but if it were...I'd probably plug in to the Assistant software and see if there is anything there that looks out of place in the parameters. You did make a paper copy of all the parameter settings, right? Stupid question...I started doing that with camera gear back in the early days of digital video, and I don't know how many times it saved my backside in that arena, so I've just carried that through to things like quads. It hasn't saved the day for me yet, but I'm sure it will at some point.

Anyway...again, if it were me and nothing looked too unusual, I'd probably try to do a fresh install of all of the up to date firmware to see if that corrects the problem.

The linking of the transmitter to the receiver of the PHANTOM was carried out before they left the factory. If necessary you can link the transmitter to the receiver as follows, for example you replace the transmitter. The default receiver type is PPM.

DO NOT use the PHANTOM transmitter (receiver) with the third party remote control equipment.

1. Please remove the housing by referring to the section of A8 Maintenance -> Remove the Housing.
2. Locate the receiver module according to the following figure.
3. After powering on the aircraft and the transmitter, if the LED indicator of the receiver on the control board is lit solid red, this means the receiver currently has no connection with any transmitter.
4. Press down the link button for more than two seconds until the LED indicator blinks, then release the button.
5. Push the throttle stick to the lowest position and turn on the transmitter. Then if the LED indicator of the receiver turns off, the link between the transmitter and the receiver has succeeded. (Linking operation can be done only when the LED indicator of the transmitter changes to blinking red .)
Note:

If the transmitter can’t enter the linking mode, please check that the throttle stick lies in the lowest position.
You can use your R/C system normally only after the linking is done successfully.